In the packing or packaging sector, plants used to carry out a plurality of processes on a packaging material, such as a sheet of cardboard, are known.
Such plants comprise one or more operating stations provided with tools, for example creasing or cutting tools, or other, of an adjustable type.
Upstream of the operating stations, with respect to the direction of feed of the sheet, this type of plant provides a loading apparatus which comprises a storage and feed store, in which at least a pallet of sheets of packaging material is disposed, means to pick up and transport the material from the store, and a device for loading the material into the operating stations.
In particular, known loading devices comprise a single feed roll, which extends along the width of the device and moves the strip forward toward the operating stations and one or more trays, each of an adjustable width, and able to guide the sheet in a precise and predefined way, toward the feed roll.
The adjustment of the width of the tray and of the position of the tools has to be carried out on each occasion in the case of a change in the format size of the sheet, thus entailing long preliminary equipping times.
The adjustment operations are long and laborious and require the stations to be stopped.
Moreover, the storing of the material in the store needs a predetermined positioning of the pallet, so that the material, when it is picked up by the pick-up and transport means, is specifically centered and aligned with the tray and with the tools.
This type of known loading apparatuses, having long preliminary equipping times, are mainly applied in productions of dimensionally predefined series of sheets, in a high and repetitive number.
There is an ever-growing need in the market to process series of sheets that are limited in number and very varied in size.
The known loading apparatuses, having long preliminary equipping times to pass from one dimensional series to another, are not used in the production of small series with different dimensions.
Machines are also known which comprise a store divided into a plurality of sectors, each of which contains a specific pallet of sheets of a determinate size.
In this known solution, a plurality of trays are provided, each fed by a corresponding sector, and selectively moved to carry the relative sheet to the feed roll.
In this solution too it is necessary to position the pallets, each in the relative sector, in a predetermined position of specific centering and alignment with the trays. Moreover, all the sectors are sized according to the widest sheet to be processed even if they contain a sheet which is decidedly smaller, and are thus, for the most part, over-sized.
Purpose of the present invention is to make an apparatus and perfect a method for loading a relatively rigid material, which allows to load in sequence series of sheets, even of a limited number, having different dimensions with respect to each other and that allows to reduce the equipping time and to optimize the use of the storage spaces.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.